Compact source of energetic sub-nanosecond red pulses based on cascaded quasi-phase-matching in aperiodically poled lithium niobate.

We present a simple, compact source of sub-nanosecond pulsed red radiation, based on cascaded nonlinear optical processes-degenerate optical parametric generation and sum-frequency generation-performed with a sample of aperiodically poled lithium niobate pumped by passively Q-switched 1.064 µm Nd:YAG laser. This system does not require feedback from an optical cavity; a single pass of the short pump is all that is required to obtain the cascaded processes, which shortens the output pulse. When pumped with a 1.2 ns, 75 µJ pulse, we obtain 670 ps pulses centered around 709 nm with an energy of 2.8 µJ, corresponding to a peak power of over 4 kW. A numerical model that predicts qualitatively the main characteristics of this source is also presented.